Most mechanical force applying devices that apply a load to a captured member do not provide a purely normal force. Frictional effects influence the force vector, such that the load that is applied usually travels with the surface of the member. Therefore, the load deviates from an ideal normal condition.
The present invention seeks to provide an apparatus for applying a pure normal or radial load. This is accomplished by applying a frictionless, normal or radial force through a fluid (liquid or air) bearing interface disposed at one end of a biasing cylinder and preferably spherically or cylindrically shaped. The bearing interface resembles a ball and socket arrangement in the preferred embodiment. A table fixture comprises four of the biased cylinders. Each cylinder is disposed ninety degrees apart, within a 360 degree radius. The fixture provides a force that simulates a pull force, often applied in a field test to a specimen (e.g., one or more fiber optic cables, a photo detector, or other component or components to be tested).
The specimen is clamped inside the fixture. A load is applied by extending each cylinder, in turn, in serial fashion, while the other cylinders remain retracted about the 360 degree radius of the fixture. No torsional force can be applied by this fixture, owing to the frictionless condition provided by the bearings. The bearings also allow the specimen to deflect in a vertical plane (parallel to the longitudinal axis of rotation).